The human foot is subjected to continuous and often excessive force every day and in every form from simply the weight of the body when standing to the extra stress of vigorous exercise and sports. Anatomically, the support provided by the foot for the rest of the body is channeled through three points, namely, the heel and at opposite sides of the ball of the foot. Normally, such support is adequate. However, certain conditions of the human body require increased cushioning and augmentation or modification of the support joints in order to maintain proper foot posture.
Conditions that require such increased cushioning and modified support are often the result of a change in a person's overall body center of gravity or balance as well as an increase in weight. Commonly, such a change occurs in women during the course of nine months of pregnancy. As a woman's weight increases and her center of gravity or balance point changes, her posture alters and stress is placed on the feet differently resulting in fatigue, muscle soreness and conditions, such as strained plantar fascia. Related conditions will include thigh and back pain as well as stress on the knees, all of which are directly connected to changes in foot posture.
Similar conditions are evident in excessively obese people or those suffering from excessive or improper spinal curvature or deformities which results in the body weight being improperly distributed through the foot and an incorrect gait when walking or running.
It is well accepted that walking is excellent exercise, particularly for pregnant women and persons of excessive weight for whom other forms of exercise may be difficult or dangerous. However, the increase in weight experienced by such individuals has an adverse effect on their foot posture and gait that discourages even walking in general much less as a form of exercise. Prior insoles have been devised to provide added support or cushioning to the feet for a variety of purposes and conditions; however, they tend toward providing a continuous cushion from the heel through the entire span of the metatarsals or individual cushions extending beyond the range of the primary gait points. None have targeted only the primary tripodal gait points of the feet as the key support points.
For example, Hara, in U.S. Pat. No. 1,210,066, provides an arch support insole of substantially continuous padding from a centrally thickened heel portion through a substantially narrowed portion on the outside edge of the cuneiform bones to a transverse portion across the first through the fifth metatarsals. In this instance support is provided primarily under the heel and the first and fifth metatarsals.
Ratcliff, in U.S. Pat. No. 2,221,202, provides a cushion support having three distinct cushions in a linear arrangement along the axis of the foot. A heel cushion extends forward to underlie the entire heel area and is of uniform thickness in its body area. An arch cushion extends beneath the mid-portion of the foot including the cuboid bone and the cuneiform arch. This cushion provides support for the three cuneiform bones, the scaphoid and cuboid bones, the rearward ends of the five metatarsals and a portion of the forward end of the os calcis. A third cushion provides support under the metatarsals and primarily the mid-sections of the 2nd through 4th metatarsals.
Hiss, in U.S. Pat. No. 2,426,735, provides a stabilizing pad insert for shoes which is formed of different densities of rubber to provide a single pad having heel, cuboid and metatarsal cushioning. The heel portion includes a flange extension and raised area designed to throw the weight laterally toward the firm portion of the pad beneath the cuboid bone while the forward portion is arched and extends transversely across the area beneath the metatarsal heads.
Looney, in U.S. Pat. No. 4,408,402, provides a shoe or shoe insert which serves to provide increased support at four specific areas of the foot through the three trimesters of a woman's pregnancy. The four support areas are the heel, directly under the longitudinal arch and longitudinally under the big and little toe of each foot.
When walking, forces are directed through three gait points forming a tripodal arrangement on the plantar surface of the foot; the posterior calcaneus, the calcaneal-cuboid area and the base or posterior end of the first metatarsal bone. It has been found that, by providing increased cushioning and support to only these three specific points, it is possible to attain a near functionally perfect gait even for those whose body weight or conditions tend to disrupt their overall foot posture.
It is therefore an object of this invention to provide a means for cushioning the plantar surface of the foot in such a manner as to induce proper posture to the foot.
It is a further object to provide a means wherein cushions are arranged in a tripodal manner relative to the underside of the foot.
It is a still further object to provide cushioning means at the locations of the posterior calcaneus, the calcaneal-cuboid area and the base of the first metatarsal bone forming a tripodal support network for the foot.
It is another object to provide an insole that is removable from a shoe and which has cushioning means at the three specified points.
And it is still another object to provide an insole of this nature which may be an integral part of a shoe.
And it is a still further object to provide a shoe incorporating a tripodal support network in its construction.